Membrane-mediated induction and sorting of K-Ras microdomain signaling platforms

J Am Chem Soc. 2011 Feb 2;133(4):880-7. doi: 10.1021/ja107532q. Epub 2010 Dec 9.


The K-Ras4B GTPase is a major oncoprotein whose signaling activity depends on its correct localization to negatively charged subcellular membranes and nanoclustering in membrane microdomains. Selective localization and clustering are mediated by the polybasic farnesylated C-terminus of K-Ras4B, but the mechanisms and molecular determinants involved are largely unknown. In a combined chemical biological and biophysical approach we investigated the partitioning of semisynthetic fully functional lipidated K-Ras4B proteins into heterogeneous anionic model membranes and membranes composed of viral lipid extracts. Independent of GDP/GTP-loading, K-Ras4B is preferentially localized in liquid-disordered (l(d)) lipid domains and forms new protein-containing fluid domains that are recruiting multivalent acidic lipids by an effective, electrostatic lipid sorting mechanism. In addition, GDP-GTP exchange and, thereby, Ras activation results in a higher concentration of activated K-Ras4B in the nanoscale signaling platforms. Conversely, palmitoylated and farnesylated N-Ras proteins partition into the l(d) phase and concentrate at the l(d)/l(o) phase boundary of heterogeneous membranes. Next to the lipid anchor system, the results reveal an involvement of the G-domain in the membrane interaction process by determining minor but yet significant structural reorientations of the GDP/GTP-K-Ras4B proteins at lipid interfaces. A molecular mechanism for isoform-specific Ras signaling from separate membrane microdomains is postulated from the results of this study.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Guanosine Diphosphate / metabolism
  • Guanosine Triphosphate / metabolism
  • Influenza A virus / metabolism
  • Isoenzymes / chemistry
  • Isoenzymes / metabolism
  • Lipid Metabolism
  • Membrane Microdomains / chemistry
  • Membrane Microdomains / metabolism*
  • Microscopy, Atomic Force
  • Models, Molecular
  • Protein Structure, Tertiary
  • Proto-Oncogene Proteins p21(ras) / chemistry
  • Proto-Oncogene Proteins p21(ras) / metabolism*
  • Signal Transduction*
  • Spectroscopy, Fourier Transform Infrared
  • Unilamellar Liposomes / chemistry
  • Unilamellar Liposomes / metabolism


  • Isoenzymes
  • Unilamellar Liposomes
  • Guanosine Diphosphate
  • Guanosine Triphosphate
  • Proto-Oncogene Proteins p21(ras)